1. Field of the Invention and Prior Art
The invention relates to a method for inhibiting exudation or blooming in flame-retardant polyolefin compositions and to an exudation inhibited flame-retardant polyolefin composition.
In the known art of flameproofing olefins, halogen donor compounds, together with antimony oxide, and sometimes other oxides for reduction of afterglow, are incorporated into the olefinic polymer. The greater percentage of these halogen donor compounds have a high-melting point or are polymeric. Therefore, they themselves act as fillers and are compatable with the system and as such do not tend to exude to the surface.
When halogen donors which have a relatively low-melting point and which are incompatable with the system are employed, there is a tendency for them to migrate to the surface during the processing or use of the flameproofed polymer. These particular additives are very efficient for flameproofing purposes and are cost effective. However, due to the poor compatability and dispersion qualities, they tend to migrate to the surface and thus impair both the surface appearance and the flameproofing effectiveness of the composition.
The invention accordingly is directed to improvements in flameproofed polyolefinic compositions in which there is a tendency for the flame retardant to exude from the surface, and is directed to a method for inhibiting this exudation.
In accordance with U.S. Pat. No. 3,730,929, the tendency toward exudation or "blooming" can be minimized by incorporating a saturated fatty acid or metal salt thereof. The results obtained, however, have not been wholly satisfactory.
It has been proposed in U.S. Pat. No. 4,006,118 that the problem can be reduced by changing the molecular structure of the organo metal retardant. But this, too, has not been entirely satisfactory and is not a solution to the existing problem.
The problem also has been attacked by incorporating a "dispersant" to effect proper dispersion of the flame retardant in the resin matrix. See, for example, U.S. Pat. No. 3,403,118. This, too, has not been entirely satisfactory.